Swab cup structures



Sept. 24, 1963 -r. c. WALDROP SWAB cuP STRUCTURES Filed April 24,. 1961 INVENTOR. TOM C. WALDROP BY Q ATTORNEYS United States Patent 3,104,595 SWAB CUP STRUCTURES Tom C. Waldrop, Arlington, Tex., assignor to Empire Rubber Co., Grapevine, Ten, a corporation of Texas Filed Apr. 24, 1961, Ser. No. 105,210 6 Claims. (Cl. 92241) This invention relates to improvements in swab cups for use in wells and more particularly relates to improvements whereby, in cases where two or more swabs are run in tandem into a well, the fluid pressure and therefore the lifting effort will be uniformly distributed among all the cups.

Usually a well operator connects at least two swab-cup supporting mandrels in tandem, although three or four in tandem is not unusual depending upon the difiiculty of the task to be performed thereby. However, when using the swab cup assemblies available on the market at present, the uppermost cup does substantially all of the lifting and the other cups merely travel therebelow to back up the upper cup in case it should wear out and fail, the lack of wear in the lower cups being attributable to the fact that these cups are not bearing the weight of the fluid column. Subsequently, when the cups are pulled from the well for inspection and/or replacement, it is common practice to discard not only the top and badly worn cup, but also the other cups connected in tandem therewith even though the latter may not be badly Worn, such waste being tolerated as a precautionary measure in view of the fact that the expense involved in removing cups from the well far exceeds the cost of the cups themselves.

It is an object of this invention to provide improved cup structures having means for distributing the lifting effort and the wear among all of the tandem cups by partially unloading the upper cups into the other cups therebelow, such partial unloading taking place at all times between the cups in one form of the invention, or alternatively in another form of the invention, occurring only after the upper cup is loaded to such a degree as to cause severe and rapid wear if not partially unloaded.

"It is another object of this invention to provide means for controlling the distribution of loading among the cups to predetermined degrees under various conditions of loading. In particular, each cup should gradually release fluid at a controlled rate into the next lower cup, either continuously, as stated above, or after the loading on the higher cup exceeds a certain unit value. 'This release of fluid takes place at the lower end of the cup, and occurs because of the novel structure of the cup itself and the cooperation of this structure with that of the cupsupporting mandrel.

Another object of this invention is to provide improved cup structures which permit the well fluids to leak oil from the bottom of the cup for the purpose of flushing out sand from the inside of the cup, which sand tends to accumulate therein, sometimes to such an extent that the cup gets stuck on the supporting mandrel and can no longer perform seating-and-unseating valve action thereon when the assembly is raised and lowered in the well bore, as is usual in the prior art.

Other objects and advantages of this invention will become apparent during the following discussion of the drawing wherein: I

FIG. 1 is an elevation view partly in cross-section of several tandem-coupled mandrels carrying swab cups built according to the invention into a well casing;

FIG. 2 is a sectional vie-w through a swab cup according to the present invention;

FIG. 3 is a partial section view through a swab cup generally similar to the cup illustrated in FIG. 2 but having a modified lower periphery; and

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FIG. 4 is a partial section view through still another modified form of the swab cup.

Referring now to the drawing, two mandrels M are shown coupled together inside a length of casing C, the mandrels generally being supported on a string of drill pipe, on a sucker rod, or even on a wire line (not shown). The upper ends of the mandrels include couplings K which screw onto the threaded lower ends T of the next higher mandrel or other supporting member. These mandrels are well known in the prior art and therefore require no further explanation.

Located on each mandrel M above the next lower coupling K is a swab cup 1 according to the invention, the general details of the swab cup being similar to others known in the prior art, each swab cup generally comprising a rubber body 2 having a bore therethrough including a larger upper bore 2a and a smaller lower bore 2b through which the mandrel M passes, the shoulder between the upper and lower bores interfering with the shoulder M on the mandrel M so as to retain the swab cup in the vicinity of the fluted portion F of the mandrel, this assembly providing the above mentioned valving ac tion by permitting well fluids to bypass the cup when the mandrel is being lowered in the well with the two shoulders in mutual contact but substantially sealing the bottom of the cup against the next lower coupling K when the mandrels are raised in the well with the cups expanded into contact with the casing C to raisethe column of'liquid therein. All of this action is well known in the prior art. Each of the cups is preferably provided with wire reinforcements 3 embedded in the outer cylindrical periphery of the cup in any suitable manner, the

.lower ends 3:: of these wires 3 being pivotally captivated by a ring 4 near the base of the cup adjacent the lower bore 2b thereof.

The improvements to which the present invention is particularly directed are located at the lower peripheries of the cups illustrated in the various modifications. The cups shown in FIGS. 1 and 2 are substantially identical with respect to these details, these cups having scalloped lower peripheries 5 which may or may not follow the contour of the reinforcing Wires at their lower ends 3:1, as at 5a in FIG. 2. By scalloping the lower surfaces 5, these surfaces are divided into surface portions which rest on the shoulder of the coupling K and into other surface portions spaced thereabove and providing passageways 5a between the cup and the upper transverse surface of the subjacent coupling K, as best illustrated in FIG. 1. The action of these passageways 5a is such as to permit a small amount of well fluid to escape therethrough substantially continually, which escape has a tendency to flush sand from within the cup which sand would normally accumulate in the bottom of the cup between the mandrel and the bore 2b. It should be apparent from FIG. 1 that only a relatively small amount of sand need be present to'clog the sliding engagement of the cup on the mandrel and thereby prevent the valving action referred to above. The loss of a small amount of swab fluid is of no significance in vie-w of the fact that 100% recovery is never realized during actual swabbing of the well in any event, a figure nearer or being considered usual. Moreover, by permitting leakage of the fluid from the upper cups it is apparent that pressure can be equalized in the spaces between each upper cup, FIG. 1, and the next lower cup.

The bottom cup in a tandem series may be made in the usual prior-art mariner so as to prevent leakage if desired, or may be made in the manner illustrated in the present figures soas to permit leakage for the purpose of flushing out sand from inside the lowermost cup. In any event, the providing of thepassagewaysSa does tend to unload the uppermost cup more than it tends to unload the lowermost cup because of the fact that the fluid pressure on the uppermost cup will tend to be greater than the pressure on each lower cup. This is because of the fact that part of the lifting pressure is relieved from the lower cup by each of the cups thereabove during the lifting action, the proportion of pressure depending-upon the proportion of lifting effort carried by the upper cup as compared with the cup therebelow. On the other hand, the cup supporting the greatest pressure has its passageways restricted to the greatest extent by axial compression of the bottom of the cup against the shoulder, and therefore tandem cups will tend to leak about equally, i.e. the cup supporting the greatest pressure will have the smallest passageways.

In the embodiment of the cup shown in FIGS. 1 and 2, the scallops can either be shaped deeply enough in the axial direction of the cup so that no amount of pressure from above -will compress the rubber sufficiently to entirely close the passageways, or alternatively, the scallops may be made shallower so that when a cup is subjected to very great axial loading the passageways will tend to be closed by axial upward compression of the rubber between the scallops. This latter type of operation will be more fully discussed below in connection with FIG. 4.

Referring again to FIG. 2, the placement of the scallops 5a between the reinforcement members so that the passageways principally occupy sectors of the cup body located between the wires has the advantage of permitting the wires to limit the compressional tendency of the rubber between the scallops. In other words, each wire 3a will back up the thicker portions of the scallops and thereby provide an abutment which limits the relative downward motion of the cup against the upper surfaceof the coupling K. The result of this limiting action is that when as much rubber has been compressed as possible below the lower ends 3a of the wires, the cup has effectively bottomed against the upper surface of the coupling K and will not move downwardly any further with respect thereto. At this time, if the passageways between the wires are shaped so deeply that they are still open, leakage is permitted even when the cup is actuially compressed against the upper surface of the coupling K as far as possible.

Referring now to FIG. 3, this modification is based on a similar general cup structure including a body portion 29 having an upper bore 28a and a lower bore 2% and reinforced by wires 3 captivated at their lower ends in an annular ring 4. However, the rubber at the lower sur-;

faces of the cup illustrated in FIG. 3 at 22 is not scalloped, but on the other hand, is stepped as at 23 so that the rubber at the transverse surface portions 24 extends downwardly further below the lower ends 3a of the wires, than does the rubber at the surface portions 25 located radially [further out at the lower periphery of the cup 20.

The cup shown in FIG. 3 operates difierently from that shown in FIGS. 1 and 2, the type of cup of FIG. 3 being substitutable for the type of cup shown in FIG. 1 on the mandrel M. This modified type of cup does not leak any fluid at low pressure or at intermediate pressures, because the rubber 24 effects a good seal against the upper surface of the coupling K at low and intermediate pressures. However, as the downward pressure is increased on the cup 26, eventually the pressure becomes so great as to be within the range which causes severe wear and perhaps even rupturing of the cup, Under these very high pressure conditions, the cup of FIG. 3 is intended to blow outwardly at the portions of the rubber 24 which are located between the Wires 3, vand especially at the locations designated by the reference numeral 26. In other words, if pressure [from the cup is relieved outwardly at the lower periphery of the cup, it will be by blowing outwardly the portions of the rubber 24 located between the wires rather than the portions of the rubber 24 located in radial alignment with the wires 3 which latter portions are reinforced by the wires. Obviously, for a particular hardness 'of rubber at the lower periphery of the cup, for particular proportions of the rubber, and for particular annular spacings between the wires 3, a certain minimum pressure will be required within the cup in order to blow outwardly by displacing the rubber of the portion 24 by raising it out of contact with the upper surface of the coupling K. a

Finally, referring to the cup shown in FIG. 4, a still further modification is provided in the basic cup including reinforcing wires 3 captivated in an annular ring 4 within a rubber body 30 having an upper bore 30a and a lower bore 39b. However, in this modified cup the lower periphery of the cup is a combination of the features of FIGS. 2 and 3 including both scalloping and narrowing .of the radial extent of the rubber at the lower periphery of the cup. In this modification, the lower periphery 32 of the cup is scalloped as at 32a, these scallops having their maximum downward extent at 34 below the lower peripheries 3a of the wires 3 and being scalloped upwardly in the vicinity of the spaces between an nularly adjacent reinforcement wires 3. Moreover, there is a step 33 at the lower periphery dividing the rubber into an axially thicker portion 3-inear the inner portion of the lower periphery and an axially thinner outer portion 35 of said lower periphery. By this means, a cup having still further novel action is provided, wherein, under light pressure, the cup leaks continuously, under intermediate pressure the cup seals against the upper surface of the coupling K by squashing the lowermost portions of the scallops 34 until the passageway portions 32a also come into contact with the upper surface of the coupling 7 K. Above this intermediate pressure at which the cup is sealed, the cup can again be forced to leak by blowing the rubber located between the wires 3,'in the vicinity marked 32b, outwardly and/ or raising it from the upper surface of the coupling K. Thus, a cup can be built which leaks at low pressure, seals at intermediate pres:

sure, and then leaks again when the pressure exceeds 2.

predetermined value so as to protect the cup by partially unloading it into the annulus therebelow and pre sumably into another cup connected in tandem 'Wlb'hflihfl one presently considered.

This cup has the advantage that it leaks at low pres- V sures to clean the sand out of the sliding engagement between the mandrel M .and the cup, it then seals at normal; and reasonable working pressures so as to carry the load i for which it was designed, and then in the presence of excessive unit pressures unseals again and permits leak age of fluid to unload some of the pressure into the cup therebelow and share its load with this cup so that two cups are used to raise the load which is normally Slip ported by only the upper cup according to the prior art.-

I have therefore provided three novel cup structures including the cup of FIG. 2 which leaks at all times at a controlled rate, or alternatively, depending upon its proportion, leaks .at low pressures but seals at high pressures;

intended operating pressures so as to share its load with' the nextlower cup and thereby protect itself from exces sive wear or rupture.

I do not limit my invention to the exact form shown in the drawing, for obviously changes may be made therein within the scope of the following claims.

'I claim:

' 1.In well-swabbing equipmenuthe combination of" mandrel means having a transverse annular shoulder; and a resilient swab cup mounted on the mandrel means above the shoulder, the cup having an axial bore therethrough for receiving said mandrel means and having an annular lower end including first transverse surface portions abut,-

ting the shoulder and supporting the cup thereon and including second transverse lower surface portions adjacent to said first portions but spaced above the shoulder when the cup is in substantially relaxed condition, said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup.

2. In well-swabbing equipment, the combination of mandrel means having a transverse annular shoulder; and a resilient swab cup mounted on the mandrel means above the shoulder, the cup having an axial bore therethrough for receiving said mandrel means and having an annular lower end including first transverse surface portions abutting the shoulder and supporting the cup thereon and including second transverse lower surface portions adjacent to said first portions but spaced above the shoulder when the cup is in substantially relaxed condition, the cup including an annular series of axially disposed reinforcing wires embedded in the body of the cup and terminating at their lower ends just above the lower end of the cup, said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup with each of said first portions located directly below a wire and said second portions located therebetween.

3. In well-swabbing equipment, the combination of mandrel means having at least two transverse annular shoulders mutually spaced apart axially of the mandrel means; and a resilient swab cup mounted on the mandrel means above each shoulder and having an axial bore therethrough for receiving said mandrel means and at least the uppermost cup having an annular lower end including first transverse surface portions abutting the shoulder and supporting the cup thereon and including second transverse lower surface portions adjacent to said first portions but spaced from the shoulder when the cup is in substantially rel-axed condition, said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup.

4. In well-swabbing equipment, the combination of mandrel means having at least two transverse annular shoulders mutually spaced apart axially of the mandrel means; and a resilient swab cup mounted on the mandrel means above each shoulder and having an axial bore therethrough for receiving said mandrel means, and at least the uppermost cup having an annular lower end including first transverse surface portions abutting the shoulder and 45 2,837,347

supporting the cup thereon and including second transverse lower surface portions adjacent to said first portions but spaced from the shoulder when the cup is in substantially relaxed condition, .at least one of the cups including an annular series of axially disposed reinforcing wires embedded in the body of the cup and terminating at their lower ends just above the lower end of the cup, said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup with each of said first portions located directly below a wire and said second portions located therebetween.

5. A well-swab cup comprising an annular body of resilient material having an axial bore therethrough, the lower end of the body including first and second transverse lower surface portions disposed at diiferent axial elevations and adjacent to each other, said first surface portions being compressible toward said second surface portions by axial forces applied against the bottom of the cup, and said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup.

6. A well swab cup comprising an annular body of resilient material having an axial bore therethrough, the lower end of the body including first and second transverse lower surface portions disposed at different axial elevations and adjacent to each other, said first surface portions being compressible toward said second surface portions by axial forces applied against the bottom of the cup, and the cup including an annular series of axially disposed reinforcing wires embedded in its body and terminating at their lower ends just above the lower end of the cup, said first and second surface portions being alternately disposed in adjacent sectors around the lower end of the cup with each of said first portions located directly below a wire and said second portions located therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,600,210 Ashton Sept. 21, 1926 1,650,099 Smith et a1. Nov. 22, 1927 2,000,109 Tyler May 7, 1935 2,518,275 Bowerman Aug. 8, 1950 Losey May 19, 1959 

1. IN WELL-SWABBING EQUIPMENT, THE COMBINATION OF MANDREL MEANS HAVING A TRANSVERSE ANNULAR SHOULDER; AND A RESILIENT SWAB CUP MOUNTED ON THE MANDREL MEANS ABOVE THE SHOULDER, THE CUP HAVING AN AXIAL BORE THERETHROUGH FOR RECEIVING SAID MANDREL MEANS AND HAVING AN ANNULAR LOWER END INCLUDING FIRST TRANSVERSE SURFACE PORTIONS ABUTTING THE SHOULDER AND SUPPORTING THE CUP THEREON AND INCLUDING SECOND TRANSVERSE LOWER SURFACE PORTIONS ADJACENT TO SAID FIRST PORTIONS BUT SPACED ABOVE THE SHOULDER WHEN THE CUP IS IN SUBSTANTIALLY RELAXED CONDITION, SAID FIRST AND 